1. Field of the Invention
The present invention relates to a communication technology, and it particularly relates to a radio apparatus that receives signals containing predetermined information.
2. Description of the Related Art
Road-to-vehicle communication has been under investigation in an effort to prevent collision accidents of vehicles on a sudden encounter at an intersection. In a road-to-vehicle communication, information on conditions at an intersection is communicated between a roadside unit and an in-vehicle unit. Such a road-to-vehicle communication requires installation of roadside units, which means a great cost of time and money. In contrast to this, a vehicle-to-vehicle (inter-vehicular) communication, in which information is communicated between in-vehicle units, has no need for installation of roadside units. In that case, current position information is detected in real time by GPS (Global Positioning System) or the like, for instance, and the position information is exchanged between the in-vehicle units. Thus it is determined on which of the roads leading to the intersection the driver's vehicle and the other vehicles are located. In order to warn the owner of a mobile terminal that a moving object is approaching him/her, the signals sent from the moving object are received by the mobile terminal. For example, the mobile terminal detects the presence of the moving object from the received signals and measures the distance between his/her own mobile terminal and the moving object, based on the receiving strength of the signals.
It is desired that such warning be given as early as possible.